Production of cyclic molecules during the γ‐irradiation of linear polydimethylsiloxane

Tanny, G. B.; Pierre, L. E. St.

doi:10.1002/pol.1971.110091111

Cited by 16 publications

(10 citation statements)

References 2 publications

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“…These are likely the result of radiation induced backbiting reactions observed in previous studies of radiation induced degradation of siloxane polymers [5,6,[26][27][28][29][30][31][32][33][34][35][36][37][38][39]. It has been postulated that recombination of the two types of polymer radicals pSi and pSiCH 2 can lead to three types of crosslinks [5].…”

Section: Resultsmentioning

confidence: 94%

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Maxwell¹,

Chinn

Alviso

et al. 2009

Polymer Degradation and Stability

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a b s t r a c tRadiation induced degradation in a commercial, filled silicone composite has been studied by SPME/GC-MS, DMA, DSC, swelling, and multiple quantum NMR. Analysis of volatile and semi-volatile species indicates degradation via decomposition of the peroxide curing catalyst and radiation induced backbiting reactions. DMA, swelling, and spin-echo NMR analysis indicate an increase in crosslink density of near 100% upon exposure to a cumulative dose of 250 kGray. Analysis of the sol fraction via Charlesby-Pinner analysis indicates a ratio of chain scission to crosslinking yields of 0.38, consistent with the dominance of the crosslinking observed by DMA, swelling and spin-echo NMR and the chain scissioning reactions observed by MS analysis. Multiple quantum NMR has revealed a bimodal distribution of residual dipolar couplings near 1 krad/s and 5 krad/s in an approximately 90:10 ratio, consistent with bulk network chains and chains associated with the filler surface. Upon exposure to radiation, the mean CU d D for both domains and the width of both domains increased. The MQ-NMR analysis provided increased insight into the effects of ionizing radiation on the network structure of silicone polymers.

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Section: Resultsmentioning

confidence: 94%

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Maxwell¹,

Chinn

Alviso

et al. 2009

Polymer Degradation and Stability

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“…Depolymerization can be catalytically or non‐catalytically driven depolymerization from a strong electrophile or a nucleophile (25–110 °C), catalytic depolymerization (110–350 °C), thermal depolymerization (over 350–500 °C) and radical scission and calcination (over 500 °C) 125 . The catalysts or catalytic activity involved in depolymerizations of siloxanes are mainly Lewis or Brønsted acids and bases, 49 organo‐metallic catalysts, 126 alcohols 127,128 and radiation 129,130 . Overall depolymerization mechanisms in siloxane systems are based on the degradation process (temperature, oxidative or reductive atmospheres, sample mass and geometry) and the network architecture (structure and chemical makeup) 131,132 .…”

Section: Introductionmentioning

confidence: 99%

Degradation of silicone‐based materials as a driving force for recyclability

Rupasinghe

Furgal

2021

Polymer International

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Siloxane polymers are an important industrial commodity based on the structure –(R2–Si–O)–. Scission of the siloxane bond is essential, as it is the first step leading to polymerization or the depolymerization of polymers into smaller units for potential recycling. These highly condition‐specific reactions selectively trigger whether polymerization or breakdowns occur and have been extensively studied over the past 80 years. However, studies to recycle siloxanes are still in their infancy. Traditional methods to synthesize silicones involve high capital‐intensive and environmental costs using carbothermal reduction. These reactions cause the excessive release of global warming gases such as CO2 and other pollutants into the environment. Therefore, being able to reuse and recycle them in a meaningful manner is highly sought. As a result, ways to controllably rupture the siloxane bond into known products have been a goal of siloxane researchers since the 1950s. Hydrolysis, catalytic depolymerization, thermal depolymerization and radical extractions are the main approaches to imbue the scission of the siloxane bond, resulting in a slew of products, including new polymers, cyclics or monomeric silanes. The present review summarizes the available published data on the degradation and depolymerization of polysiloxanes published up to July 2021. © 2021 Society of Industrial Chemistry.

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“…In these early studies, the polymers used were copolymers of acrylic acid containing minor quantities (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) mol % ) of naphthylmethyl methacrylate (NMMA) which were end-trapped with anthracene to demonstrate the efficiency of energy transfer. In these early studies, the polymers used were copolymers of acrylic acid containing minor quantities (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) mol % ) of naphthylmethyl methacrylate (NMMA) which were end-trapped with anthracene to demonstrate the efficiency of energy transfer.…”

Section: Discussionmentioning

confidence: 99%

“…18 The distribution of distances between sites is Gaussian with one-dimensional variance given1* by u2 = C,n12/3, where n is the number of repeat units between sites, C, is the characteristic ratio, and 1 is the length of one repeating unit. Here, M , is the number-average molecular weight of the primary chains, p is the density of the network, N A is Avogadro's number, and V, is the volume fraction of polymer in the system.…”

Section: Computer Modelmentioning

confidence: 99%

Computer simulations of radiation-cured networks

Shy¹,

Eichinger²

1986

Macromolecules

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Simultaneous cross-linking and chain scission reactions that are induced by ionizing radiation have been simulated with a computer. These studies were performed for both bulk-and solution-cured poly(dimethylsi1oxane) (PDMS) systems. Variations of network structures and mechanical properties that depend on the degree of cross-linking are presented. It is shown that radiation-cured networks are barely connected and contain large amounts of defect structures. More than 90% of the defects are found to be dangling ends, and isolated ends are dominant in this population. The weight fraction of loops is quite small, but they deplete a large fraction of the cross-links. These results are in good agreement with experiment and with other calculations. Potential correlations between network structures and the Mooney-Rivlin coefficients 2C1 and 2C2 are also discussed.ABSTRACT Partial sulfonation of poly(2-vinylnaphthalene) (P2VN) yields water-soluble copolymers (SP2VN) that appear to exhibit hypercoiling in aqueous media. Luminescence emission studies show that excimer emission

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Production of cyclic molecules during the γ‐irradiation of linear polydimethylsiloxane

Cited by 16 publications

References 2 publications

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Degradation of silicone‐based materials as a driving force for recyclability

Computer simulations of radiation-cured networks

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